The present invention relates generally to the measurement of railroad track stiffness in the vertical plane and more particularly to a dynamic track stiffness measurement system and method for the repetitive measurement of railroad track position and deflection under load from a moving measurement vehicle.
In the past, a variety of measuring devices have been developed to sense and measure various features of a railroad track. U.S. Pat. Nos. 5,654,511 to Sugino et al. and U.S. Pat. No. 5,756,903 to Norby et al. illustrate known static and dynamic track measuring devices and methods. However, one track feature, deflection under load in the vertical plane has proven difficult to measure accurately under any condition and particularly difficult to measure in a continuous, dynamic manner.
With the advent of high speed rail corridors, accurate measurements of track stiffness in the vertical plane along the length of the corridor are a key to building and maintaining reliable track condition and performance data for the corridor. Since both lightweight, highspeed trains and slower, heavy freight trains are likely to pass over the same tracks in the high speed corridor, the effect on the rails, the cross tie ballast and the subgrade layers varies with the traffic thereby making track degradation in the corridor a variable which must be monitored if proper track maintenance is to be achieved.
In vertical plane track stiffness measurement, it is critical that resolution be high. This requires a stable reference plane from which track position and vertical deflection can be determined as a function of track loading. In the past, static wayside measuring techniques have been used with the ground adjacent the track as a static reference relative to which track deflection under load in the vertical plane is measured by spaced transducers or other measuring devices positioned at selected locations. Using this technique, only limited sections of the track along a corridor are sensed, and a multiplicity of static transducers are required making this technique expensive. U.S. Pat. No. 4,701,866 to Harrison et al. discloses a static analog measuring system for measuring wheel loads at selected locations along a track.
It is a primary object of the present invention to provide a novel and improved method and apparatus for dynamically measuring a railroad track condition using a railroad reference platform to create a line of sight reference relative to which the position of the track is measured.
Another object of the present invention is to provide a novel and improved method and apparatus for dynamically measuring a track condition using a railroad reference platform from which a reference plane is created and taking a plurality of spaced, successive measurements of track position relative to the reference plane as the railroad reference platform moves along the track.
A further object of the present invention is to provide a novel and improved method and apparatus for dynamically measuring railroad track condition using a railroad reference truck from which a reference plane is created and a second track reference which measures the distance between the track and a target. This second track reference may be a second railroad truck spaced from the railroad reference truck. The second railroad truck carries a target, and the position where the reference plane contacts the target is used to obtain a track geometry and performance measurement.
Yet a further object of the present invention is to provide a novel and improved method and apparatus for dynamically measuring a railroad track condition using a railroad reference truck from which a reference plane is created and a second railroad truck spaced from the railroad reference truck. A first track condition measurement is made relative to the reference plane when the reference truck is over a point in the track and a second track measurement is made relative to the reference plane when the second railroad truck is over the same point in the track.
A further object of the present invention is to provide a novel and improved method and apparatus for dynamically measuring a railroad track condition using a first railroad reference truck from which a first reference plane is created, a second railroad truck spaced from the first railroad reference truck, a second railroad reference truck from which a second reference plane is created, and a third railroad truck spaced from said second railroad reference truck. A load is applied to said third reference truck, and a first track condition measurement is made relative to the first reference plane when said second railroad truck is over a point in the track. A second track condition measurement is made relative to the second reference plane when the third railroad truck is over the same point in the track.
These and other objects of the invention are achieved by creating a reference line or plane from a reference railroad truck that is the same or parallel to a plane extending through the center of the wheels of the reference railroad truck. The reference plane is created preferably by an optical beam source, a video camera, or an electromagnetic beam source mounted on the reference railroad truck that is directed to a target mounted on a second, loaded railroad truck spaced from the reference railroad truck. Alternatively, a mechanical walking beam can be used to create the reference plane. A measurement indicative of the distance between the reference plane and the railroad track is taken when the reference truck is over a point in the track and a second measurement indicative of the distance between the reference plane and the track is taken when the loaded railroad truck is over the same point in the track. These measurements can be taken using a first reference truck and a first target bearing truck on a reference railroad car or a reference loaded portion of a long railroad car and a second reference truck and a second target bearing truck on a second loaded railroad car or a load bearing portion of a long railroad car.